The present invention relates to a laser probe for use in ophthalmic procedures and more particularly to a multi-spot laser probe for use in photocoagulation.
Anatomically, the eye is divided into two distinct parts—the anterior segment and the posterior segment. The anterior segment includes the lens and extends from the outermost layer of the cornea (the corneal endothelium) to the posterior of the lens capsule. The posterior segment includes the portion of the eye behind the lens capsule. The posterior segment extends from the anterior hyaloid face to the retina, with which the posterior hyaloid face of the vitreous body is in direct contact. The posterior segment is much larger than the anterior segment.
The posterior segment includes the vitreous body—a clear, colorless, gel-like substance. It makes up approximately two-thirds of the eye's volume, giving it form and shape before birth. It is composed of 1% collagen and sodium hyaluronate and 99% water. The anterior boundary of the vitreous body is the anterior hyaloid face, which touches the posterior capsule of the lens, while the posterior hyaloid face forms its posterior boundary, and is in contact with the retina.
Macular degeneration is a medical condition predominantly found in elderly adults in which the center of the inner lining of the eye, known as the macula area of the retina, suffers thinning, atrophy, and in some cases bleeding. This can result in loss of central vision, which entails inability to see fine details, to read, or to recognize faces. According to the American Academy of Ophthalmology, it is the leading cause of central vision loss and in the United States today for those over the age of fifty.
When blood vessels beneath the retina bleed, a form of macular degeneration, called wet macular degeneration, results. In some cases, this bleeding may be halted or slowed using a procedure known as photocoagulation. Photocoagulation is a technique employed by retinal surgeons to treat a number of eye conditions, one of which is the exudative (wet) form of macular degeneration. In this treatment, laser light rays are directed into the eye focusing on abnormal blood vessels that are growing beneath the retina. This laser cauterizes the vessels to seal them from further leakage in the hope of preventing further vision loss.
Using a standard laser probe with one emitted beam spot, the ophthalmic surgeon typically turns the laser beam off and on in rapid fire succession with a foot pedal as he scans the beam across the retinal surface to create a one-dimensional or two-dimensional array of photocoagulated laser burn spots on the retina. It can take a long time to cover the desired retinal area with photocoagulated spots using a single-beam laser probe.
A multi-spot laser probe can potentially reduce the time required to create the desired pattern of laser burn spots. However, given a laser with limited laser beam power that is already operating at its maximum laser power setting, a multi-spot laser probe may not necessarily reduce the time required to create the desired laser burn spot pattern. This is because the fixed laser power P is divided between N beam spots so the power in a given beam spot is on average only P/N. Therefore, to create an equivalent burn, the required exposure time is roughly N times the exposure time for a single-beam laser probe. Therefore, although there are only 1/N the required number of laser fires from a single beam probe, the exposure time per beam fire is N times that of a single beam probe. So the overall time to lay down the array of burn spots remains the same.
However, there are now available new photocoagulation lasers such as the Alcon Laboratories, Inc.'s NGL (Next Generation Laser) whose desired beam intensity to create an ideal photocoagulation spot is a small fraction f of the maximum available beam intensity. If f is equal to 1/N, then a multi-spot laser beam with N emitted beams can be used with the laser beam at maximum power level and the overall time to create the desired coagulation spot patterns is only 1/N of the time required with the single-spot laser probe. This reduces the overall time for each operation and enables more operations to be performed in a given day, causing the overall cost per operation to be reduced. Therefore, it would be desirable to have a multi-spot laser probe for performing photocoagulation.